The development of HIV vaccines and other prevention strategies relies on the use of nonhuman primates in preclinical studies to advance the development of effective AIDS vaccine candidates and to advance development of effective topical microbicides and other prevention modalities or immune-based therapies. The NIAID Simian Vaccine Evaluation Unit (SVEU) contracts shall provide nonhuman primate resources that primarily support preclinical evaluation of AIDS vaccines. The SVEUs conduct studies in support of vaccines being developed by a wide range of investigators. These studies complement NIAID-supported basic vaccine research and vaccine evaluation studies funded through R01 (investigator-initiated research) grants, HIVRAD (HIV Vaccine Research and Design Program) grants, IPCAVD (Integrated Preclinical-Clinical AIDS Vaccine Development) grants, and NHP Consortium awards. The SVEUs also perform studies of candidate vaccines offered by companies or other researchers. The primary activity is to conduct an in vivo SHIV or SIV titration via mucosal route in non-human primates.